初次接触d3.js，能感觉到它的强大，想要完全搞懂还是要花一番功夫，最近用它画了个折线图作为入门，以后还要多学习，请大家指教。
这个例子是在网上找到的，然后自己看懂这些代码的意思，小调整了一下，作为笔记出现，方便下次参考。
首先看一下效果图：
image.png
以下为源代码：
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>d3折线图</title>
<script src="https://cdn.bootcss.com/jquery/3.2.1/jquery.min.js"></script>
<script src="d3.v3.min.js"></script>
<style>
body {
font: 10px sans-serif;
margin: 50px;
}
.grid .tick {
stroke: lightgrey;
opacity: 0.7;
shape-rendering: crispEdges;
}
.grid path {
stroke-width: 0;
}
.axis path {
fill: none;
stroke: #bbb;
shape-rendering: crispEdges;
}
.axis text {
fill: #555;
}
.axis line {
stroke: #e7e7e7;
shape-rendering: crispEdges;
}
.axis .axis-label {
font-size: 14px;
}
.line {
fill: none;
stroke-width: 1.5px;
}
.dot {
/* consider the stroke-with the mouse detect radius? */
stroke: transparent;
stroke-width: 10px;
cursor: pointer;
}
.dot:hover {
stroke: rgba(68, 127, 255, 0.3);
}
</style>
</head>
<body>
<div id="trendSvg"></div>
</body>
<script type="text/javascript">
var data = [
[{'x':1,'y':0},{'x':2,'y':5},{'x':3,'y':10},{'x':4,'y':0},{'x':5,'y':6},{'x':6,'y':11},{'x':7,'y':9},{'x':8,'y':4},{'x':9,'y':11},{'x':10,'y':2}],
[{'x':1,'y':1},{'x':2,'y':6},{'x':3,'y':11},{'x':4,'y':1},{'x':5,'y':7},{'x':6,'y':12},{'x':7,'y':8},{'x':8,'y':3},{'x':9,'y':13},{'x':10,'y':3}],
[{'x':1,'y':2},{'x':2,'y':7},{'x':3,'y':12},{'x':4,'y':2},{'x':5,'y':8},{'x':6,'y':13},{'x':7,'y':7},{'x':8,'y':2},{'x':9,'y':4},{'x':10,'y':7}],
[{'x':1,'y':3},{'x':2,'y':8},{'x':3,'y':13},{'x':4,'y':3},{'x':5,'y':9},{'x':6,'y':14},{'x':7,'y':6},{'x':8,'y':1},{'x':9,'y':7},{'x':10,'y':9}],
[{'x':1,'y':4},{'x':2,'y':9},{'x':3,'y':14},{'x':4,'y':4},{'x':5,'y':10},{'x':6,'y':15},{'x':7,'y':5},{'x':8,'y':0},{'x':9,'y':8},{'x':10,'y':5}]
];
var colors = [
'steelblue',
'green',
'red',
'purple'
];
var margin = {top: 20, right: 30, bottom: 30, left: 50},
width = 960 - margin.left - margin.right,
height = 500 - margin.top - margin.bottom;
var x = d3.scale.linear()
.domain([0, 12])
.range([0, width]);
var y = d3.scale.linear()
.domain([-1, 16])
.range([height, 0]);
//x轴设置
var xAxis = d3.svg.axis()
.scale(x)
.ticks(10)//调节刻度大小
.tickSize(-height)
.tickPadding(10)
.tickSubdivide(true)
.orient("bottom");
//y轴设置
var yAxis = d3.svg.axis()
.scale(y)
.tickPadding(10)
.tickSize(-width)
.tickSubdivide(true)
.orient("left");
//缩放拖拽
var zoom = d3.behavior.zoom()
.x(x)
.y(y)
.scaleExtent([-10, 10])//可缩放的范围
.on("zoom", zoomed);
var svg = d3.select("#trendSvg").append("svg")
.call(zoom)
.attr("width", width + margin.left + margin.right)
.attr("height", height + margin.top + margin.bottom)
.append("g")
.attr("transform", "translate(" + margin.left + "," + margin.top + ")");
svg.append("g")
.attr("class", "x axis")
.attr("transform", "translate(0," + height + ")")
.call(xAxis);
svg.append("g")
.attr("class", "y axis")
.call(yAxis);
svg.append("g")
.attr("class", "y axis")
.append("text")
.attr("class", "axis-label")
.attr("transform", "rotate(-90)")
.attr("y", (-margin.left) + 10)
.attr("x", -height/2)
.text('Axis Label');
svg.append("clipPath")
.attr("id", "clip")
.append("rect")
.attr("width", width)
.attr("height", height);
var line = d3.svg.line()
.interpolate("linear")
.x(function(d) { return x(d.x); })
.y(function(d) { return y(d.y); });
svg.selectAll('.line')
.data(data)
.enter()
.append("path")
.attr("class", "line")
.attr("clip-path", "url(#clip)")
.attr('stroke', function(d,i){
return colors[i%colors.length];
})
.attr("d", line);
var points = svg.selectAll('.dots')
.data(data)
.enter()
.append("g")
.attr("class", "dots")
.attr("clip-path", "url(#clip)");
points.selectAll('.dot')
.data(function(d, index){
var a = [];
d.forEach(function(point,i){
a.push({'index': index, 'point': point});
});
return a;
})
.enter()
.append('circle')
.attr('class','dot')
.attr("r", 2)
.attr('fill', function(d,i){
return colors[d.index%colors.length];
})
.attr("transform", function(d) {
return "translate(" + x(d.point.x) + "," + y(d.point.y) + ")"; }
);
function zoomed() {
svg.select(".x.axis").call(xAxis);
svg.select(".y.axis").call(yAxis);
svg.selectAll('path.line').attr('d', line);
points.selectAll('circle').attr("transform", function(d) {
return "translate(" + x(d.point.x) + "," + y(d.point.y) + ")"; }
);
}
</script>
</html>
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